1,2,4-Thiadiazol-3,5-diyl-sulfenamides

ABSTRACT

1,2,4-Thiadiazol-3,5-diyl-sulfenamides and thiosulfenamides of the formula   in which x is one or two, R and R&#39;&#39; are hydrogen, alkyl, aralkyl, cycloalkyl, or together with the nitrogen atom to which they are attached form a heterocyclicamino radical are excellent accelerators and vulcanizing agents for the vulcanization of rubber.

United States Patent [1 1 Harman Aug. 12, 1975 l,2,4-THlADIAZOL-3,5-DIYL- I SULFENAMIDES [75] Inventor: Marion W. Harman, Dunbar, W.

A [73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed: May 14, 1973 21 Appl. No.: 359,978

[52] US. Cl. 260/302 SD; 260/5; 260/243 B; 260/247.l; 260/293.63; 260/785; 260/786 [Sl] Int. Cl C07d 91/60 [58] Field of Search 260/302 SD, 247.1, 293.63, 260/243 B Primary Examin'erRichard J. Gallagher [5 7] ABSTRACT l,2,4-Thiadiazol 3,S-diyl-sulfenamides and thiosulfenamides of the formula V in which x is one or two, R and R are hydrogen, alkyl, aralkyl, cycloalkyl, or together with the nitrogen atom to which they are attached form a heterocyclicamino radical are excellent accelerators and vulcanizing agents for the vulcanization of rubber.

a 7 Claims, N0 Drawings l.2.4-THIADIAZOL-3.S-DIYL-SULFENAMIDES BACKGROUND OF THE INVENTION This invention relates to di(sulfenamides) and di(thiosulfenamides) of 1,2,4-thiadiazoles.

Many azole sulfenamides are known, for example substantialuquantities of benzothiazole sulfenamides are used as accelerators in the vulcanization of rubber. Attempts at replacing the benzothiazole radical with other azole moieties have not been commercially suc cessful either because the proposed azole intermediates were too expensive or because the resulting sulfenamide failed to possess adequate vulcanization properties, or both. A class of 1,2,4-thiadiazole sulfenamides has been discovered which are potentially inexpensive and exhibit adequate processing safety and potent accelerator activity.

SUMMARY OF THE INVENTION According to this invention, compounds characterized by the formula in which x is one or two, R and R independently are hydrogen, alkyl of l-8 carbon atoms, aralkyl of 7-10 carbon atoms, cycloalkyl of -8 carbon atoms, or R and R together with the nitrogen atom to which they are attached form a heterocyclicamino radical of 4-8 carbon atoms are excellent accelerators and vulcanizing agents for rubber. A preferred group of compounds comprises compounds in which R is hydrogen and R is alkyl, aralkyl or cycloalkyl and especially important members of this group are compounds in which R is tert-butyl, benzyl or cyclohexyl. A more preferred group of compounds comprises compounds in which R and R along with the nitrogen atom form a heterocycle and especially compounds with heterocyclicamino radicals containing six ring members. Compounds in which x is one are accelerators for the vulcanization of rubber and compounds in which at is two are accelerators and vulc'anizing agents meaning that they accelerate the vulcanization of rubber in the presence of other vulcanizing agents and will cross-link rubber by themselves when other vulcanizing agents are not present.

The terms asused herein and in the claims mean as follows: Alkyl means a branched or unbranched saturated acyclic radical derived by removal of one hydrogen atom from an alkane. Alkyl radicals of l-8 carbon atoms are satisfactory, for example, methyl, ethyl, pro- I pyl; isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl,

pentyl, hexyl, l-methylhexyl, heptyl, and octyl. Aralkyl means phenyl substituted alkyl with radicals of 7-10 carbon atoms being satisfactory and benzyl being pre ferred. Other aralkyl radicals are a-methylbenzyl, oca-dimethylbenzyl, xylyl, phenethyl, phenylpropyl and icals are cyclopentyl, cyclohexyl, Z-methylcyclohexyl,

4-methylcyclohexyl, cycloheptyl, and cyclooetyl.

Heterocyclicamino means the radical derived by re moval of hydrogen from the nitrogen atom of a cyclic amine. Thus, R and R are joined to each other and along with the nitrogen atom form a heterocyclic ring. It is understood that R and R may be joined to each other through carbon forming a mono or bicyclic alkylene radical or may be joined to each other through oxygen or sulfur forming a single divalent radical attached to the nitrogen comprising two alkylene radicals interrupted by oxygen or sulfur. Examples of satisfactory heterocyclicamino radicals are pyrrolidinyl, 2,5-dimethylpyrrolidinyl, piperidino, 4-methylpiperidino, 2,6- dimethylpiperidino, 2,4,6-trimethylpiperidino, 2- ethylpiperidino, morpholino, thiomorpholino, 2,6- dimethylmorpholino, hexahydro- 1 H-azepinl -yl and azabicyclo(3.2.2)non-3-yl.

Illustrative examples of compounds of the invention are: 3,5-di( N-methylaminothio)-l ,2,4-thiadiazole, 3,5-

di( N,N-dimethylaminothio)-1 ,2,4-thiadiazole, 3 ,5- di( N-ethylaminothio)-l ,2,4-thiadiazole, 3,5-di(N,N- diethylaminothio l ,2,4-thiadiazole, 3 ,5-di( N- isopropylaminothio)-1,2,4-thiadiazole, 3 ,5-di(N,N-

diisopropylaminothio )-1 ,2,4-thiadiazole, 3 ,5 -di( N-tertbutylaminothio)-1,2,4-thiadiaz0le, 3,5-di( N- benzylaminothio )-1 ,2,4-thiadiazole, 3 ,5-di( N- cyclohexylaminothio)-l,2,4-thiadiazole, and the corresponding thiosulfenamides.

Further illustrative examples of compounds of the invention are 3,5-di(pyrrolidinylthio)-l ,2,4-thiadiazole, 3 ,5-di( 2,S-dimethylpyrrolidinylthio )-l ,2,4-thiadiazole, 3 ,5-di( piperidinothio l ,2,4thiadiazole, 3 ,5-( 2,6- dimethylmorpholinothio)- l ,2,4-thiadiazole, 3 ,5- di( hexahydro-l H-azepinl ylthio 1 ,2,4-thiadiazole, 3,5-(azabicyclo( 3.2.2)non-3-ylthio)- l ,2,4-thiadiazole, 3,5-di(pyrrolidinyldithio)- l ,2,4-thiadiazole, 3,5-di( 2,5-

dimethylpyrrolidinyldithio l ,2,4-thiadiazole,' 3,5- di( piperidinodithio l ,2,4-thiadiazole, 3 ,5-di( 2,6- dimethylmorpholinodithio )-l ,2,4-thiadiazole, 3,5-

di( hexahydrol l-l-azepinl -yldithio )-l ,2,4-thiadiazole, and 3,5-di(azabicyclo( 3.2.2)non-3-yldithio)-l ,2,4- thiadiazole.

The sulfenamides of this invention are used in the same manner as conventional accelerators. They are incorporated into the rubber by addition to an internal mixer, such as a Banbury mixer, or they may be added to the rubber on a mill. The fully compounded stocks are then heated to effect vulcanization. The amount of accelerator used varies depending upon the properties desired in the vulcanizates but generally is between 0.2-6.0 parts by weight per parts by weight of rubber with 0.5-2.0 parts by weight per 100 parts by weight of rubber being the amount normally used. However, when the thiosulfenamides of the invention are used as vulcanizing agents, 2.0-5.0 parts by weight per 100 parts by weight of rubber are generally used.

The rubber stocks may include conventional compounding ingredients such as carbon blacks, zinc oxide, reinforcing silica, stearic acid, extender oils, phenolic antidcgradants, phenylenediamine antidegradants, tackifiers, scorch inhibitors and bonding agents and may also include conventional accelerators. Elemental sulfur is commonly the vulcanizing agent but any sulfur=containing vulcanizing agent which at cure temperature'or below releases sulfur in the form, available to cross=link rubber is suitable. Illustrative sulfur vulcanizing agents are amine disulfldes, for example, dimorpholinodisulfide; and polymeric polysulfides, for example, alkyl phenol disulfide.

For the rubber stocks tested and described herein as illustrative of the invention, Mooney scorch times at the designated temperatures are determined by means of a Mooney plastometer. The time in minutes required for the Mooney reading to rise five or ten points above the minimum viscosity is recorded. Longer times on the Mooney scorch test are desirable because this indicates greater processing safety. Cure characteristics are determined at the designated temperatures by means of the Monsanto Oscillating Disk Rheometer which is described by Decker, Wise and Guerry in Rubber World, December 1962, page 68. From the Rheometer data, the maximum torque, R max., in Rheometer units is recorded. The increase in torque is a measure of the degree of vulcanization and is proportional to the crosslink'density. The time 1 in minutes for a rise of two Rheometer units above the minimum reading and the time, 1 required to obtain a torque of 90% of the maximum are recorded. The difference, r 4 is a measure of the cure rate of the sample. Vulcanizates are prepared by press curing at the selected temperature for the time indicated by the Rheometer data to obtain optimum cure. The physical properties of the vulcanizates are measured by conventional methods.

DESCRlPTlON OF PREFERRED EMBODIMENTS diate for the preparation of other sulfenamides by reaction with an amine to remove the NH as by-product ammonia and introduce the amine moiety in its place. Another method comprises reaction of 1,2,4- thiadiazol-3,S-diyl-sulfenyl chloride with amine in the presence of a hydrogen chloride acceptor. The intermediate sulfenyl chloride is prepared by chlorinating an alkali metal salt of 3,5-dimercapto-1,2,4-thiadiazole as described by Thaler and McDivitt, J. Org. Chem., Vol. 36, pp. 14-17, 1971. Also, the methods known for preparing thiosulfenamides are applicable to the preparation of the thiosulfenamides of this invention. In general, the methods involve insertion of sulfur into the sulfenamide corresponding to the desired dithiosulfenamide. A procedure hereinafter described comprises reacting 1,2,4-thiadiazol-3,S-diylsulfenamide and sulfur with amine.

l,2,4-thiadiazol-3,S-diyl-sulfenamide is prepared by the following procedure:

A solution of dipotassium salt of 2,6-dimercapto- 1,2,4-thiadiazole is prepared by heating at 50-60C. for 30 minutes 145.8 grams of potassium cyanodithioimidocarbonate and 24.1 grams of sulfur in 400 ml. of water and 400. m1. of methanol. The solution is cooled to room temperature before use. The solution of dipotassium salt of 2.5-dimercapto-l,2,4-thiadiazole and a solution of 983 grams of sodium hypochlorite 13.64 g NaOCl/ 100 g 11:0) are simultaneously added with stirring over a one-hour period at 05C. to 6000 ml. of concentrated ammonium hydroxide (88.7 moles of NH OH). After stirring one additional hour at 05C., the reaction mixture is filtered, washed with Water until neutral and air-dried at 25-30C. l,2,4-thiadiazol-3,5- diyl-sulfenamide, m.p. 99l00C., is recovered in 67% yield. Chemical analysis gives 13.30% C, 2.17% H, 30.97% and 53.56% S compared to 13.32% C, 2.24% H, 31.08% N and 53.36% S calculated for C H N S Identification is confirmed by nuclear magnetic resonance spectral analysis.

Morpholine (78.6 grams) is added at 25-30C. in one portion to a stirred slurry comprising 54.1 grams of 1,2,4-thiadiazol-3,S-diyl-sulfenamide in 150 ml. of methanol. The mixture is stirred for 24 hours. A clear solution and ammonia evolution is observed in about one-half hour and after about three hours a precipitate forms. The mixture is cooled to 0C., stirred for onehalf hour at 0l0C. and the precipitate recovered by filtration and airdried at 2530C. 3,5- Di( morpholinothio )-1 ,2,4-thiadiazole, m.p. 106107C. recrystallized from alcohol, is recovered in 91% yield. Chemical analysis gives 37.27% C, 4.95% H, 17.30% N, 10.45% 0 and 30.02% S compared to 37.47% C, 5.03% H, 17.48% N, 9.99% 0 30.02% S calculated for C H N O- S Identification is confirmed by nuclear magnetic resonance spectral analysis.

A stirred slurry comprising 18 grams of 1,2,4- thiadiazol-3,5-diyl-sulfenamide, 6.4 grams of sulfur and 26.2 grams of morpholine in ml. of methanol is heated at reflux (6065C.) for 1.5 hours. After cooling to 30C., ml. of petroleum ether is added and mixture stirred for one hour at 25-30C. The solids are recovered by filtration and air-dried at 25-30C. 3,5- Di(morpholinodithio)-1,2,4-thiadiazole, m.p. 133134C. recrystallized from isopropanol, is obtained in 81% yield. Chemical analysis gives 30.91% C, 4.02% H, 14.31% N, 9.09% O and 41.92% S compared to 31.23% C, 4.19% H, 14.57% N, 8.32% O and 41.69% S calculated for C H N O S Identification is confirmed by nuclear magnetic resonance spectral analysis.

Ammonium chloride (26.8 g) and cyclohexylamine (62.5 g) in 250 m1. of isopropanol are added with stirring at room temperature to an aqueous solution of the sodium salt of isoperthiocyanic acid. The salt solution is previously prepared by digesting at 50C. for 15 minutes xanthane hydride (37.6 g) and 25% NaOH (81 g;

0.505 mole). The mixture is stirred for 15 minutes during which time the temperature rises to 32C. Sodium hypochlorite solution (485 ml., 0.885 mole, 13.59 g NaOCl/ 100 g H O) is added dropwise over a period of 135 minutes while maintaining the temperature between .4050C. After determining by iodine-starch paper that the reaction is complete, the sample is aciditied with dilute acetic-acid and any excess NaOCl is neutralized by adding 5 g of sodium sulfite. The reaction mixture is stirred for one hour, cooled to 20C., and 300 ml. of water is added dropwise. An oil layer forms which is extracted with 300 ml. of ether, washed with water, washed with 1% acetic acid solution, and then washed with water until neutral. The solvent is removed by heating in vacuo for 2 hours at 60C. Forty grams of 3.5-di(cyclohexylaminothio l ,2,4 thiadiazole. an amber solid, is recovered. Chemical analysis gives 16.75% N and 25.12% S compared to 16.26% N and 27.92% S calculated for C H N S The following tables illustrate the use of the compounds of this invention as accelerators and vulcaniz- Stock 1 is a control stock containing a known accelerator and Stock 2 is a stock containing an accelerator of this invention. Comparison of the data indicates that 3 .5-di( cyclohexylaminothio l ,2,4-thiadiazole has ing agents in the vulcanization of rubber. Natural rub- 5 about the same accelerator potency as the known acber masterbatches are prepared by mixing the ingredicelerator but exhibits more processing safety. Similar ents shown below in standard rubber mixing equipevaluations with l,2,4-thiadiazol-3,S-diyl-sulfenamide All Parts are y Welght Santoflex 13 15 shows that it is a potent but somewhat scorchy accelery y "P y -P-P y and ator. Vulcanizates prepared from vulcanizable compo- Neozone D is N-phenylB-naphthylamine. Vulcaniz- 1O sitions comprising styrene-butadiene rubber and comable compositions are prepared by adding sulfur and pounds of this invention exhibit satisfactory physical sulfenamide of this invention or by just adding thiosulti fenamide of this invention to portions of the master- Al h h th invention h b ill d b i l batch. The properties of the vulcanizable compositions examples, it is not limited thereto. Changes and modifiand of the vulcanizates are determined as previously 15 cations of the examples of the invention herein chosen explamed. for purposes of disclosure can be made which do not constitute departure from the spirit and scope of the Musterhatch 1 Masterhatch 2 mventlon' Ingredient Parts by weight Parts by weight The embodiments of the mvention in which an exclu- Natural rubber l 000 I000 sive prlvilege or property is clalmed are defined as fol- Zinc oxide 3.0 3.0 lows- Stewc acld l. A compound of the formula ISAF Carbon black 45.0

HAF Carbon black 50.0 R

Hydrocarbon softener 5.0 3.0 N (5)J-CN Neozone D 1.0 R 1| 11 /R Santoflex 13 2.0 N C(S),N I

TOTAL 1570 159.0

TABLE 1 Stock 1 2 3 4 5 Maisterl utch 1 157.11 157.1) 157.0 157.11 157.0 Sulfur 2.1) 2.11 1.0 1.11 5.5Di(inurphulilinlhiu)- 11.5 1.0

1 .IJ-thizidinlole ,5I)i(murpholinodithiu)- 0.5 H) 31) l.I.4-lhi:1t|i;1/ulc Mount Scorch :11 Z50F t minutes 44.7 25.5 35.7 31 I Rhcumcter data at 292F R m;1\. 400 321K .18. 1 38.6

1, ms 36.0 2&3 201) um, 311.5 2*).7 17 7 10,1 Stress-Strain tilllll :11 38F ('urc time. minutes 61) 6(1 45 31111"; Modulus. psi 11120 1111111 10411 10411 L It. tensile. psi 2550 2491) 2650 2950 Rhuoxnclur till! 11! 3291.

Stocks 14 illustrate the accelerating properties at in which x is one or two, R and R independently are different accelerator-sulfur ratios of a sulfenamide and hydrogen, alkyl of 1-8 carbon atoms, aralkyl of 7-10 thiosulfenamide of the invention. The data indicate carbon atoms, cycloalkyl of 58 carbon atoms, or R that both are powerful accelerators of vulcanization and R together with the nitrogen atom form pyrrolidiand that the sulfenamide possesses superior processing nyl, 2,5-dimethylpyrrolidinyl, piperidino, 4- safety. Stock 5 demonstrates that the thiosulfenamide methylpiperidino, 2,6dimethylpiperidino, 2,4-6- is a potent vulcanizing agent in the absence of sulfur. trimethylpiperidino, 2-ethylpiperidino, morpholino,

thiomorpholino. 2,6-dimethylmorpholino, hexahydro- 5S lH-azepin-l-yl or azabicyclo(3.2.2)non-3-yl.

2. The compound of claim 1 in which x is one.

3. The compound of claim 2 in which R and R are TABLE 11 hydrogen 4. The compound of claim 2 in which R is hydrogen St k and R is cyclohexyl. 1 2 5. The compound of claim 2 in which Masterbatch 2 159.0 159.0 R Sulfur 3.5 2.5 \R, 2-Mercaptohcnzothiuzole 0 5 3.5Di(cyclohexylaminothioJ 0.5 5 mol'pholmov 1 2,4-thitidiazn|e 6. The compound of claim 1 in which .r is two.

i s c W 4 7 8 z 7. The compound of claim 6 in which s i ress strain data at 292] N R Cure time. minutes 60 60 \R' 3005? modulus. psi 2290 2100 3x00 3540 1S morpholmo- Ult. tensile, psi 

1. A COMPOUND OF THE FORMULA
 2. The compound of claim 1 in which x is one.
 3. The compound of claim 2 in which R and R'' are hydrogen.
 4. The compound of claim 2 in which R is hydrogen and R'' is cyclohexyl.
 5. The compound of claim 2 in which
 6. The compound of claim 1 in which x is two.
 7. The compound of claim 6 in which 